How to open system console to get output from Blender on Mac OS 10?
Right click on the Blender icon in the Applications folder and select "Show Package contents". Make an alias of Contents/MacOS/Blender by right clicking and selecting "Make Alias". Rename it and move it somewhere you like.

This opens the console in the background, next to the Blender application.

source:
https://www.lynda.com/Blender-tutorials/Set-up-Blender-console-window/486043/533594-4.html